The present invention is directed to a stable hair care composition and, in particular, to a stable shampoo composition comprising a surfactant, a fatty alcohol, a non-volatile silicone, and a critical amount of a polymeric suspending agent, wherein the polymeric suspending agent is the sole suspending agent for suspending the silicone in the composition. The polymeric suspending agent is a polymer that is substantially free of any crosslinking, e.g., a non-crosslinked polymer. The present invention also relates to a method of suspending silicone in a water-based shampoo matrix using a non-crosslinked polymeric suspending agent.
The use of silicones in shampoo compositions has been disclosed in a number of different patents: U.S. Pat. No. 3,964,500 to Drakoff, U.S. Pat. No. 4,364,837 to Pader, U.S. Pat. Nos. 4,788,006 and 4,902,499 to Bolich, Jr. et al., U.S. Pat. No. 5,034,218 to Duvel, and U.S. Pat. No. 5,409,695 to Abrutyn et al. A major problem associated with formulating a shampoo composition containing silicone is the instability of the composition. A particularly difficult problem in silicone-containing shampoos is that of keeping a dispersed, insoluble, non-volatile silicone material suspended in stable form while retaining the performance properties of the shampoo.
Attempts to overcome such instability have been made. For example, it is known to stabilize silicone by using one or more of triethanolamine or triethanolamine compounds such as triethanolamine stearate, ethylene glycol distearate and stearamine. Additionally, U.S. Pat. No. 5,034,218 teaches that anionic surfactants and cationic conditioning agents are compatible, when combined with an anionic polymeric suspending agent, to suspend non-volatile silicone in the composition. In particular, this patent discloses a stable conditioning shampoo composition having an anionic surfactant and a cationic quaternary nitrogen-containing conditioning agent with a non-volatile silicone suspended therein using an anionic, crosslinked polymeric suspending agent such as a crosslinked polyacrylic acid suspending agent. The polyacrylic acid is an anionic crosslinked material and, more importantly, is not the only suspending agent. Other suspending agents such as distearyldimonium chloride, distearyl dimethyl ammonium chloride and dicetyl dimethyl ammonium chloride are also included.
A publicly available shampoo contains a non-crosslinked material, namely an acrylate/steareth-20 methacrylate copolymer, as a thickener. It is believed that this copolymer is present in minimal amounts of less than 1.00% by weight. Thus, the copolymer is not present at the critical level necessary for enhanced stability according to the present invention. This shampoo also contains other suspending agents such as triethanolamine stearate, ethylene glycol distearate and stearamine.
Rohm & Haas discloses the use of an acrylate copolymer, sold under the trade name Aculyn.RTM. 33, in an anti-dandruff shampoo. Rohm & Haas also discloses the use of an acrylate/steareth-20 methacrylate copolymer, sold under the trade name Aculyn.RTM. 22, in another anti-dandruff shampoo. These shampoos, however, do not contain any silicone. Moreover, the level of the acrylate and acrylate/steareth-20 methacrylate copolymers is less than the level found to be critical in the present invention.